Ignition timing control device



J. S. -HASBRGUCK IGNITION TI-MING CONTROL DEVICE Filed neg. 25, L1942mmm x lNvENToR John $.Hasbrouclc Patented Dec. 4, 1945 IGNITION TIMINGCONTROL DEVICE John S. Hasbrouck, Glastonbury, Conn.,'assignor to UnitedAircraft Corporation, East Hartford, Conn., a corporation of DelawareApplication December 23, 1942, Serial No. 469,931

8 Claims.

This invention relates to improvements in ignition timing controldevices for an engine equipped with a supercharger.

An object of the invention is the provision of an automatic ignitioncontrol mechanism actuated by the pressure drop across the enginesupercharger and responsive to power operating conditions of the engine.

A further object is the provision of an ignition timing control devicewhich is operative to advance the ignition timing during an intermediaterange of engine power output and to retard the timing on both sides ofthat intermediate range.

A still further object is the provision of an ignition timing deviceutilizing a simplified form of servo-motor control for adjusting thetiming according to the power output of the engine.

Other objects and advantages will be apparent from the speciiicationyand claims, and from the drawing, which illustrates what is nowconsidered to be a preferred embodiment of the invention.

In the drawing.

Fig. 1 is a diagrammatic view of a control aps paratus .constructedaccording to the invention, certain elements being shown in section tobet ter illustrate the construction thereof.

Fig. 2 is a view of a detail of one of the magneto drive gear trains, online 2-2 of Fig. 1.

Fig. 3 is a view along the line 3--3 of Fig. 2.

Fig. 4 is a view through the control valve and valve operating mechanismshown in Fig. 1 but showing a diilerent operating position"l of thevalve from the position shown in Fig. 1, and

Fig. 5 is a view similar to Fig. 4 showing an operative position of thevalve different from the positions shown in Figs. 1 and 4.

Referring to the drawing in detail, I0 generally indicates an enginesupercharger and I2 and I4 indicate a pair of magnetos which supplyelectrical energy to the engine ignition system.

The supercharger has a casing I6 with an inlet I8 and outlets 20. Theimpeller 22 is driven by a shaft 24 extending from the engine, generallyindicated at 26. Each outlet 20. is connected with the intake of anengine cylinder, in a. well known manner..

Magnetos I2 and I4 are connected with Athe engine spark plugs 80 bysuitable ignition conduits and are driven from the engine by meansvdiagrainmatically illustrated in Fig. 1 and comprising an engine drivenshaft 32, gears 34, shaft as indicated at 42 and 44, and these gearsmesh with gears 46 and 48 of gear trains 38 and 48'. As the two geartrains 38 and 40 are similar in all respects, a detailed description ofonly one of them will be suiilcient for the present purpose.

Referring to Figs. 2 and 3, gear 46 is rigidly secured to an oppositelyb'eveled gear 56 supported for free rotation on the outer end of themagneto drive shaft 52. Gear 68 meshes with a pair of idler gears 54 and56 carried by a cage 58 supported on shaft 52 which is freely rotatabletherein. Idler gears 54 and 56 mesh with a drive gear 60 secured toshaft 52 by pin 6|, The drive is therefore from shaft 36 through gears42 and 46 to gear 50 and from gear 50 through idler gears 54 and 56 togear. 60. With this arrangement, it is apparent that rotation of cage 58about shaft 52 will angularly displace gear 60 relative to gear 58resulting in an angular displacement of shaft 62 relative to enginedriven shaft 32 and a consequent change in the timing of the magnetodriven by shaft 52.

Rotational movement of the cages of both magneto gear drives,.about themagneto drive shafts, is controlled by a servo-mechanism generallyindicated at 62 and comprising a double ended piston 64 slidable inaxially aligned cylinders 66 and f 68 and connected with the cages ofthe magneto Shaft` 36 has a bevel gear at each end thereof, 55

- 'I4 and 16 extending radially from the idler gear cages 58, of geartrains 38 and 40 so that movement of piston 64 will effect a change inthe timing of the magnetos.

Within cylinder 66 is a compression spring 'I8 which urges piston 64towards its spark-retarding position against the end of a stop securedin the cylinder 68 and telescopically associated with the hollow end of'the piston 64. A somewhat similar stop 82 in cylinder 66 limits themovement of piston 64 in the spark-advancing direction. Stops 80 and 82are integral with the screw plugs which close the outer ends ofcylinders'68 and 66 respectively. Either or both stops 86 and 82 may beadiusted so that a desired spark setting may be obtained for bothretarded and advanced positions. Y

Piston 64 is moved towards spark advanced position, illustrated in Fig.1, by the application of duid under pressure through line 84 to theinterior of cylinder 68 and is moved towards spark retarded position byspring 'I8 and also by duid under pressure admitted through line 86 tothe interior of cylinder 66. The application of fluid under pressure toservo-motor 62 is controlled output of the engine.

v by a valve, generally indicated at 88. and so arranged that when iluidunder pressure is being applied through one of these lines to acylinder, the other line acts as a drain for the other cylinder.

Valve 88 comprises acylinder 80. having an intermediate port 02connected with a iluid pressure line 84, drain ports 96 and 88 spacedfrom pressure port 82 on opposite sides thereof, and ports |02 and |00for lines 84 and 88 disposed each between the pressure port and a drainport. Within cylinder 80 is a plunger |04 provided with two pistons |06and |08 controlling the connection between the above mentioned ports ina manner t'o be described. A drain is provided at Il to a sump, which isusually the engine crankcase.

Plunger |04 is operated by a flexible diaphragm ||0 mounted in a hollowcasing ||2 in such a manner as to provide a closed chamber at each sideof the diaphragm.A One of these chambers is connected through tube |4with supercharger casing I6 and the other chamber is connected through atube ||6 with the supercharger inlet I8 so that the pressuredifferential between the supercharger inlet and outlet is exerted ondiaphragm ||0 which tends to resiliently take the position illustratedin Fig. 4. A compression spring isplaced beneath diaphragm ||0 to givethe correct rate of travel in proportion to the pressure head of thesupercharger.

In Fig. 1 the diaphragm is in an intermediate position corresponding toan intermediate power In this position pistons |08 and |08 connectpressure port 82 with port |02 of line 84 thus applying pressure to theinterior of cylinder 88 to move piston 84 to the left against spring 18to a position against the end of the stop 82, thus moving arms 14 and 18to the position at which the timing of the magnetos is advanced. At thesame time, line B6 is connected with drain port 8G to vent any fluidtrapped in cylinder Si. I

Fig. 4 shows diaphragm ||0 in the position which it occupies duringidling operation of the engine when the pressure head across thesupercharger is substantially negligible. In this position the diaphragmhas raised pistons |06 and |08 to connect pressure port 82 with port |00of channel 8S thus applying fluid under pressure to the interior ofcylinder 66 to force piston 64 to its limiting position against stop 80which corresponds to the spark retarding position of the servomechanism. At the same time, line 84 is drained through port 98.

Fig. 5 shows the position of diaphragm ||0 when the engine is operatingin the upper portion of its power range. Under this condition pistons|00 and |08 connect the line 80 with the pressure line 94 through ports|00 and 92 to apply iluid under pressure to the interior of the cylinder66 thus again retarding the spark by moving piston 84 against stop 80.At the same time the line 84 is connected with the drain port 88 thusventing iluid from the cylinder 68 as indicated above in connection withFig. 4.

Since the engine power output is accurately indicatedby the pressurehead across the supercharger, it will be apparent that the apparatusabove described serves to maintain the engine ignition timing retardedduring idling and full power operation of the engine, and to advance thetiming only during the intermediate, or cruising, range of engineoutput. Thus is pro- Avided a highly sensitive and accurate automaticcontrol for regulating the timing of the engine ignition to avoiddetonation while at the same time providing the maximum efficiency andeconomy of engine operation.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as defined by the followingclaims.

I claim:

1. In combination with an engine having l. supercharger and anadjustable electric ignition system, a `servomotor for adjusting saidignition system to change the timing thereof, and means for controllingsaid servomotor including a casing, a diaphragm dividing said casinginto two separate chambers, means connecting one of said chambers withthe outlet side of said supercharger, means connecting the other chamberwith the inlet side of said supercharger. and a device actuated by saiddiaphragm for controlling said servomotor.

2. In combination with an engine having a supercharger and an adjustableelectric ignition system, a servomotor for adjusting said ignitionsystem to change the timing thereof, and means for controlling saidservomotor including a easing, a

diaphragm dividing said casing into two separate chambers, meansconnecting one of said chambers with the outlet side of saidsupercharger, means connecting the other chamber with the inlet side ofsaid supercharger, and a device actuated by said diaphragm forcontrolling said servomotor, said device having three operativepositions corresponding to three consecutive pressure ranges between theinlet and outlet of said supercharger and operative in the first andthird of said positions to maintain said servomotor in its sparkretarding position, and in the second of said positions to maintain saidservomotor to its spark advancing position.

3. In combination with an engine having a supercharger and an adjustableelectric ignition system, a servomotor for adjusting said ignitionsystem to change the timing thereof, and means for controlling saidservomotor including a casing, a diaphragm dividing said casing into twoseparate chambers, means connecting one of said chambers with the outletside of said compressor, means connecting the other chamber with theinlet side of said compressor, and a valve actuated by said diaphragmand hydraulically connected with said servomotor for maintaining saidservomotor in its spark retarding position during the high and lowranges of engine power operation and maintaining said servomotor to aspark advanced position dun'ng engine operation within a predeterminedintermediate power range.

4. In combination with an aircraft engine, an engine drivensupercharger, an electrical ignition mechanism, an adjustable timingdevice for said mechanism, and means responsive to variations in thepressure rise across said supercharger for adjusting said timing deviceincluding means for retarding the ignition timing at relatively low andhighvalues of said pressure rise and advancing the ignition timing atintermediate values of said pressure rise.

5. In a method of operating an aircraft engine having an adJustableelectric ignition system and anvengine driven supercharger, the steps ofvarying the ignition timing in accordance with variations in thepressure rise across said supercharger, comprising, automaticallyadvancing the ignition timinginresponsetoanincreaseinthepresmre riseacross said supercharger to an intermediate value and automaticallyretardi'ng vthe ignition timing in response to a further increase insaid therefor, a source of iiuid pressure. valve means for advancing orretarding the ignition timing,

and means responsive to the pressure rise directly,

across the engine superchsrger for adjusting the? valve means to retardthe ignition timing when l said pressure rise is above or below anintermediate range and to advance the ignition timing ivhen saidpressure rise is within said range.

8. In an engine having an ignition system, an

induction system and a supercharger in said infor controlling theapplication of said pressure duction system, means for adjusting theignition y timing. and means actuated by the pressure rise directlyacross said supercharger for operating said adiustingmeans. A A

- JOI-IN B. HASBROUCK.'

